JPH0627773B2 - Method of creating reference data in circuit board inspection device - Google Patents

Description

The present invention relates to a reference data creating method in a circuit board inspection apparatus.

[Conventional example and its problems]

Generally, in an in-circuit tester, non-defective product data is absorbed from a non-defective substrate, and the non-defective product data is used as reference data for pass / fail judgment. This is convenient because it is not necessary to set the reference data or the like on the program, but it has the following drawbacks.

That is, on the assumption that all the substrates which are conventionally considered to be non-defective products are true non-defective products, the data is absorbed from these substrates and averaged to form the reference data, and no particular check is performed on the data. Even if it is a non-defective board, if a relay, a switch, a semi-fixed resistor, etc. are mounted, those parts may not be arranged in the same state for some reason.

Therefore, even if the good product data is obtained from the good product substrate and the reference data is created, the reliability cannot be said to be very high.

[Means for solving problems]

In order to solve the above-mentioned conventional problems, in the present invention, prior to the board inspection, the non-defective data for each measurement point is absorbed from a plurality of non-defective boards, and the non-defective data is used as reference data as a pass / fail judgment criterion. In order to obtain, the data of the measurement points are measured for each of the non-defective boards, the measurement data is added, and the number of non-defective boards provided for measurement is counted, and the added value of the measurement data and the board Calculating a provisional average value from the number of sheets count value of, and comparing the provisional average value with the measurement data,
The true average value is calculated only for the measurement data whose difference is within a predetermined value, and the reference data as the pass / fail judgment standard is obtained based on the average value.

[Work]

According to the above method, even if the board is a non-defective board, it is significantly deviated from the tentative average value due to a setting error of the switch or semi-fixed resistor mounted on the board. High reference data is created.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, taking a circuit network composed of four resistors R1 to R4 shown in FIG. 1 as an example, a device for measuring data at respective measurement points A to D will be described.

This measuring device includes four probes 1 to 4 corresponding to the respective measuring points A to D. That is, the probe 1
For measuring point A, 2 for B, 3 for C and 4 for D
It is planted on a pin board of a fixture (not shown) so as to correspond to the above. For each probe 1-4,
Two changeover switches 1a, 1b; 2a, 2 respectively
b; 3a, 3b; 4a, 4b are connected in parallel. Each of the probes 1 to 4 has one of the switches 1a and 2
It is connected to a measuring signal source, for example, an AC voltage source 5 via a, 3a and 4a. Further, each of the probes 1 to 4 is connected to the signal detection unit 6 via the other switch 1b, 2b, 3b, 4b. In this embodiment, the signal detection unit 6 is composed of a current-voltage converter. An A / D converter 8 is connected to the output side of the signal detection unit 6 via an amplifier 7, and the converted data is processed by a CPU (central processing unit) 9, and the switches 1a-4b are also connected. This CPU9
It is controlled by.

According to this measuring device, each measuring point A is
The measured data in ~ D are absorbed. First, a non-defective substrate is set on a fixture (not shown), and a pressing device (not shown) is also operated to bring the probes 1 to 4 into contact with measurement points A to D of the non-defective substrate. Then, of the switches 1a to 4a on the AC voltage source 5 side, the switch 1a
Is set to "open", the other switches 2a to 4a are set to "open", and among the switches 1b to 4b on the signal detector 6 side,
The switch 1b is "closed" and the other switches 2b to 4b are "open". As a result, the measurement points B, C, and D have the same potential, and only the measurement point A has a low potential with respect to them. Therefore, in this example, current flows from the measurement points B and D toward the measurement point A. become. This current is converted into, for example, a voltage by the signal detector 6, and the amplifier 7
After being amplified to a predetermined value by, it is converted into digital data by the A / D converter 8. The data thus obtained is the impedance at measurement point A. Next, among the switches 1a to 4a on the AC voltage source 5 side, the switch 2a is set to "open" and the other switches 1a, 3a, 4a are set to "closed", and the switch 1b on the signal detector 6 side is set.
Among the switches 4b to 4b, the switch 2b is "closed" and the other switches 1b, 3b, 4b are "open". Thereby, the impedance of the measurement point B is measured. Thereafter, the impedances at the measurement points C and D are obtained in the same manner.
The CPU 9 sets, for example, the optimum range of the signal detector 6 for each measurement point, and the range data is stored in the memory 10.
Memorized in. That is, the optimum range is set at the time of absorbing the data from the first non-defective substrate, and the same range is applied to the second and subsequent measurement points. It is preferable to fix the range to the first one as described above in order to perform high-speed processing, but in some cases, the range processing may be performed for each substrate by the auto range.

As described above, the non-defective data (impedance) at each measurement point of the non-defective substrate is obtained. In the present invention, the reference data is obtained from the non-defective data as follows. Shows its flow chart.

For example, if 10 good boards are prepared, the data is first absorbed from all the boards. That is, the impedance data of each measurement point (A1, B1, C1, D1) is obtained from the first sheet, and similarly from the second sheet, (A
2, B2, C2, D2) ... From the 10th sheet (A10, B10,
The data C10, D10) are obtained, and the CPU 9 stores these respective measurement data in the memory 10. In addition, the number of non-defective substrates used accordingly (10 in this example)
Is counted by the CPU 9.

Next, the CPU 9 calculates a temporary average value at the measurement points from the above data. If the provisional average value of each measurement point is expressed as, A = (A1 + A2 + ... A10) / 10, B
= (B1 + B2 + ... B10) / 10, ... D = (D1 +
D2 + ... D10) / 10. Then, the provisional average value and each measurement data are compared and determined, and the data that is significantly deviated is excluded. The criterion is, for example, whether the range set when absorbing data from the first non-defective board is over or under, or a simple change amount from the tentative average value (lower limit -50%, upper limit 100% ), Or a deviation value and a standard deviation value are used. This determination result, for example, the data A at the measurement point A on the second substrate
If 2 is significantly deviated from A, the data A
2 as well as data B2 to D2 obtained from the same substrate are excluded. This is the in-circuit tester of the composite circuit,
This is because usually, if one point is defective, other points will be affected.

Thereafter, the CPU 9 performs a calculation to obtain a true average value for each measurement point from the remaining data, and the same average value is used to create reference data as a quality determination standard.

After the reference data is set as described above, the circuit board to be inspected is set on the fixture chart and the board inspection is performed. That is, the switches 1a to 4 on the side of the AC pressure source 5 according to the same order as the above switch switching order.
a and the switches 1b to 4b on the signal detector 6 side are switched to measure the impedance at each measurement point A to D on the circuit board to be inspected, and the CPU 9 compares the measured impedance with the reference data. It In this case, the reference data has a predetermined range, and if the measurement data is within the range, “GO” indicating the inspection success is displayed on the display device 11 such as CRT, and if it is out of the range, the defective product is defective. Is displayed, for example, "NG" is displayed.

〔The invention's effect〕

As described above, according to the present invention, when the good product data is absorbed from the good product substrate, the good product data itself is compared with the specific comparison reference data to select the good product substrate. Data is obtained.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a measuring device used for carrying out the present invention,
FIG. 2 is an operation flowchart of the present invention. In the figure, 1 to 4 are probes, 5 is a measurement signal source, 6 is a signal detector, 8 is an A / D converter, 9 is a CPU, and 10 is a memory.

Claims (1)

[Claims] 1. A method for creating reference data in a circuit board inspection device, which absorbs non-defective product data for each measurement point from a plurality of non-defective sub- strate boards and obtains reference data as a pass / fail judgment standard from the non-defective product data prior to the board inspection. In, the data of the measurement points are measured for each of the non-defective boards, the measurement data is added, and the number of non-defective boards provided for the measurement is counted, and the added value of the measurement data and the number of boards Calculates the provisional average value from the count value, compares the provisional average value with the measurement data, calculates the true average value only for the measurement data whose difference is within a predetermined value, and based on the average value A method for creating reference data in a circuit board inspection device for obtaining reference data as a quality judgment standard.